Implantable medical devices (IMDs) can perform a variety of diagnostic or therapeutic functions. In an example, an IMD can include one or more cardiac function management features, such as to monitor the heart or to provide electrical stimulation to a heart or to the nervous system. The cardiac function management features can be used to diagnose or treat a subject, for example, in cases of electrical or mechanical abnormalities of the heart. Examples of IMDs can include pacers, automatic implantable cardioverter-defibrillators (ICDs), cardiac resynchronization therapy (CRT) devices, implantable monitors, neuromodulation devices (e.g., deep brain stimulators, or other neural stimulators), cochlear implants, or drug pumps, among other examples.
Such IMDs can include electronic circuitry configured to wirelessly transfer information between implanted IMDs, or between an IMD and an assembly external to the body. Such information can include, for example, programming instructions or configuration information to configure the IMD to monitor, diagnose, or treat a physiologic condition. Such information can also include data sensed, detected, or processed by the IMD and transmitted to another device or assembly (e.g., physiologic information, a disease status, etc.) An IMD can include an antenna sized and shaped to wirelessly transfer information using a desired operating frequency range. Such a frequency range can be specified by a spectrum allocation authority within the country where the IMD may be located or used. Thus, the IMD generally includes an antenna tailored to the spectrum allocation regulations where the IMD may be used or sold.